Manufacture of hydrochloric acid



Aug. 30, 1932. l. c),l BARS-[Ow ET AL l Y 1,874,692

yILNUAC'JRE OF HYDROCHLORIIACID Filed 0G13. 4, 1929 ir plus Cfr/orina 7 Sham ATTORNEY Patented Aug. 30, 1932 UNITED EDWIN o. BAnsfrow ANDl s'IIIiLDoN B. HEATH, or MIDLAND, MICHIGAN,y AssIGNonsTo man Dow CHEMICAL coMreNY, on MIDLAND, MICHIGAN, A CORPORATION oiritIcII:`

IGAN MANUFACTURE or IIYD-nocrILonIc ACID l l Application aia'octoter 4, 1929; serial No.l 397,252. Y

This invention relates to Ithe manufacture of hydrochloric acid and hasparticular regardv to va process involving the combustion of a carbonaceous material in the presence of s chlorine and waterI vapor.

ln a copending application, Serial No; 397,197, filed October 14, 192,9, we have disclosed broadly a process for the manufacture ofhydrochloric acid which consists in reacting chlorine, andwater vapor `at a temperature between about 900o and 1500o ance with the equation;

in accord In theaforesaid application specific reference is made to a process wherein the reacting gases arebrought Vtogether in-a'heated reaction zone but out of direct contact with the hot gases of combustion whichare einployed for'producing the degree of temperature requisite 4for the reaction. The present application describes a; Inodeof procedure wherein the reacting gases are interinixed with the combustiongases, the: combustion of the fuel'and the formation of'hydrochloric acid taking place together,simultaneously.

Generally speaking, the process ofthe present invention is carried out by introducing chlorine and water vapor directly. into the f combustion zone. wherein the fuel; isl being burnt and then absorbing hydrochloric acid from the exit gases. ,l lhen a liquider gas Y eous hydrocarbonmaterial, such as, petrolleum or natural gas, 1s utilized the coinbustion of the hydrogen constituent thereof fur-` nishes atleast a portion of thev waterrequired to react withthe chlorinel present. Likewise, when a combustible gaseous rnixture containing` free hydrogen,1such as water gas, is burnt, the water formedvby the oxidation of hydrogen is available for reaction with the chlorine. If a carbonaceous fuel containing little or no hydrogen, such as pow-r dered coal, is used practically all of the water vapor required` is tobe introduced as such into the combustion zone. The function of the fuel consumed inthe process is primarily to supply the heat required `to maintain the temperature of the reaction, sullicient air or. oxygenbeing yintroduced therewith to eifect Vopera-,ting conditions an excess of oxygen ,is

always present during. .the"reactiimj` It is,` also essential for complete conversion of chlorinefto hydrochloric acid, atleast at the-tempera-tures. .contemplated herein, that an ex-x cess of water vapor be ernployed, preferably asrnuch as 100 to 200per ,cent excess.v vlnthe annexeddrawing v o" QL Fig. l `illustrates diagrarnmatically`y one` forni -Of yapparatus adapted to carrying 'out our new'and improved process and Fig.l 2 il-` lustrates afmodifiedforrn designed for-,the recovery of the heat in the reaction gases. o v Asa fuel suitable for usein the process we prefer a hydrocarbon material such ,as'crude petroleum or the heavy fractions thereof known as fuel oil, although `we may also'4 -ural `gas or,` mixtures of 'g such. materials` Chlorine may bej admixed ,withthe'Q ainV required for the combustion of the f oil, but particular advantage from the standpoint of cost is :secured by, utilizing i forf the urpose dilute chlorine gas mixtures which are obtained asby-productorwaste product of` various industrial processes, such dilute chlorine'having but little econolnic value for most other purposes. *The amountof water forined by the combustion of the fuel theoretically will be sufficient to combine with the chlorine introduced, but, as already stated, an. excess .of .water is required inforderfto obtainV a? ,complete conversion of lchlorine .to hydrochloride acid. Forexaniple, whenno additional water isiused- We have found that enters the reaction. Obviously, also, all or a portion of such water vapor maybe formed in situduring the reactioirby the combustion of hydrogen introduced along with.. the

gases entering the reaction. In such case air Y is to be supplied in sufficient volume to eHect the combustion of both the fuel and hydrogen, and still leave an excess of oxygen in the exitV gases. v

Referring to the drawing, Fig. 1, 1 is a furnace including a combustion chamber 2,

' open at one end and connecting at the other with a flue 3. An oil burner 4 is located at the ,openv end of chamber 2, andprovided with connections V5r for fuel oil supply and 6 for air or steam and chlorine. A separate Y,

feed pipe 7 for introducing steam is also provided. vFlue 3 leads to a cooler 8, .which in turn isconnected with the base of a scrubber Y tower'9. A water inlet 10 atY the topof tower k9 anda trapped outlet 11 from the base thereof are provided as shown. 1

Inoperating the apparatus just described, oil or other suitable fuel is atomized in burner 4 by means of air or steam introduced thereto under pressure. The chlorine, may be conveniently introduced alreadypremixed with air is maintained suicient to raise the temperature of the exitV gases preferably to from 14000 to `1500"(1. When a sufficientexcess of water vapor is present the conversion of chlorine `becomes substantially 'quantitative atsuchftemperature, and no free chlorine is found in the exit gases.` The exit gases passing out through liuc 3 vconsist of a mixture of hydrochloric acid, water vapor, carbon dioxide, oxygen and nitroger'nj They are lowered intemperaturein cooler 8 andv then conducted tothe baseof the absorption tower 9', preferablyv filled withan acid proof packing material, wherein ythey pass upwardly in countercurrent to a stream ofwater or of an aqueous hydrochloric acid solution` intro# duced into the'top of the tower through inlet 10. The hydrochloric acid is dissolved and is collected as a solution thereof in the base ofthe tower, whencethe solution is drawn ifthrough trapped outlet l1. One or more such absorption towers may be provided, depending upon the conditions necessary for obtaining a complete absorption of the acid gas. If desired', the acidsolution from the base of the tower may be recirculatedv over thetower until `any desired strength of solution is produced. v f

vAs already stated the preferred reaction temperatureis between 14000 and V115000 C.,

assuch'temperature has been found necessary, to secure complete conversion, of chlorinefto hydrochloric acid. However, a substantial reaction occurs at temperatures as low as 9000 to 10000 C., and, by recycling the l exit gases, the process may be operated at such lower temperatures with a good yield of hydrochloric acid. In such case, however, free chlorine will be present in the exit gases and will also be dissolved, in the absorbing' Vand provided interiorly with a checker work of fire brick or other'suitablegmaterial arranged in the usual way; VAninlet 3 for-air and chlorine, and an exit passage 4 for reacted gases communicate with conduits 5 and 6, respectively, connecting with chambers l and 2. Areversing valve? located at the junction of the inlet and exit passages and connect-ing conduits provides for reversing the intercommunica'ticn therebetween, as

shown. Passages 8 and 9 lead from the upper partv ofchambers 1 and 2, the lower portions thereof being separated from each ,other by means of baille wall 10, above which the passages unite to form a combustion chamber 11. Oil burners l2 and 13` are directed into passages 8 and 9, respectively, through openings providedl therefor, and are connected by means of valved pipes 14 and 15, respectively, with an oil supply and by pipes 16 and 17, respectively, for air or steam suicient to atomize the oil. Steam may be admitted to chambers 1 Vand 2 by means of valved pipes' 18 and 19, respectively.

In operating the apparatus just described in Fig. 2, .a dilute chlorine gas, or mixture of air and chlorine, containing preferably from 2 to 10 per centchlorine, is introduced through inlet 3 and conduit 5 into chamber 1, wherein it ispreheated up to about 12000 to 13000 C., at least atthe beginning of each cycle, by the heat stored in the checker'work packing from a previous operation. The preheated gases pass thence into passage 8 and combustion chamber 11 wherein they are in-` timately mixed with theburning oil vapors introduced by burner 12, the volume of such preheated gases admitted'be'ing controlled so yas to furnish anexcess over the quantity ofv air required for the complete combustion of the oil. j The temperature of the reacting gases in thecombustion'l chamber is raised to about 14000 to 15000 C., the suppliesof oil and air, respectively, being so'regulated as to maintain thel temperature within such n limits. `In order to provide the excess of water essential for a quantitative conversion, steam is conveniently introduced nearl the base of chamber 1 as shown in the drawing.`

The hotfreaction gases flow from-.combus-v Y tion chamber 11 throughv passage 9 to cham` ber 2, wherein they give up a portion of their 63T follows heat to the brick packing thereof andbecoine cooled to about 6000 F. The cooled gases then traverse conduit 6 leading to exit passage 4, which in turn conveys the gases Vdi- 8 rectly to the scrubber tower or other device for absorbing the hydrochloric acid gas therefrom. A j When the. temperature of the incoming gases entering the combustion chamber has 1 fallen to about 10000 C., valve 7 i is reversed so that the air-chlorine mixture. entering at 3 now passes upwardly through conduit 6 into chamber 2, wherein the heat'stored Vin the brick packing raises the temperaturen-f the gases entering the combustion chamber at 9 to about 13000 C. Oil 'burner 12 is turned Y olf, and burner 18 is started, likewise. steam inlet 18 is shut oft',A and steam admitted to chamber 2 at inlet 19, the further operation then continuing as vbefore except that the direction of flow of the. gasesisreversed, the cooledgases finally passing out through lconduit 5 to exit passage 4. Under continuous operation 'the direction of iiow is reversed periodically atfsuch intervals as to maintain an approximately stable temperature condition in the combustion chamber without increasing fuel consumption.

The heat regenerator chambers 1 and 2 and "T the combustion chamber are to be constructed of refractory material capable of withstanding high temperatures, and covered externally with heat insulating material. The inletfpassage 3, outlet passage 4 and conduits 5 and 6 may likewise' be, constructed Vof reor conduits is avoided, and no corrosion diffi- 5 culties are encountered. i

The following detailed examples are presentedby way of illustration of our improved process, but itis understood thatthe invention is not limited to the specific conditions of temperature, concentration, quantities of materials, etc. therein set forth.

Example 1 i 1 ,.3 In an apparatus similar to that shown in Fig. 1 of the drawing fuel oil was burnt with a chlorine-air mixture containing approxi-Y mately 8.0 per cent chlorine. The temperature in the combustion chamber was maintained between 11500 and 15400 C. The quantity of oil consumed to maintain the temperature was .214 pounds oil per pound of chlorine introduced. Anraverage analysis of the exit gases from the reaction was as required-to'balance the equation; Y

The tetalfvolume of exit gases was approximately 75 cubic feet per minute. The water Y content of the exit gases c orrespondedto about per cent in excess ofA thequantity initially 'erigoefecnfsgi-Hoieeog Under .the conditions y of .the experiment,

.21 maximum temperature of 15400 C.,v the conversion of C12 to HG1 was 80 per cent. 1 .e d l Example? i i ln this example the procedurewas similar to that iniExample 1, except that additional steam was introduced with the vcombustion gases suiiicient to provide aneexcessof 200 per cent thereof over the amount theoreti-` cally required. The chlorine-air mixture contained 8.16 per cent chlorine, vand oil consumption wasr.236 pounds per pound ofchlorine, maintaining a reactionr temperature -be Y tween 11000 and 14300 C. rI he analysis of the exit gases on adry basis was as 'follows The volume of exit gases-was A75 cubici feet per minute calculated at standard conditions.` Conversion offCl'z to `HC1 jwas 100 pel@` cent. e 1 he proportions of air, chlorine and'steam in the reaction mixture may be varied betweenV rather wide limits, v but in general the airchlorine mixture is preferably regulatedto contain from`2to 10 per cent chlorine, while sufficient steam is added to provide lan excess of `from 100 to 200 per cent above theth'eoretical .quantity of water required forthe reaction. `The preferred temperature range Withinh the combustion zone, as already stated, is between 14000 and 15000 C., although temperatures as low as -9`000 to`10000 C. ma be- Y employed. Higher temperatures than t ose above given afford no added advantage,and,if

employed, may leadto excessive deterioration of apparatus: `In practice the'quantity of fuel oil, or its equivalent, employed is determined by-the requirement for maintaining al favorable reaction temperature, and this inl turn depends measurably upon the design and thermal efficiency ofthe apparatus. "While inthe examples given the voili consumption was slightly less than one quarter pound per pound of chlorine, by utilizinga more effi-A ciently `designed apparatus embodying means for conserving heat, as 'shown'in Fig. '2, the

' the process herein disclosed, provided the ks tep lor steps stated by any of the following claims steps. l

oil consumption may be materially diminished below the Yfigures given, n n j '1 .Other types of fuel may beutilizedin place of fuel oil, such as crude oil,tar or lighter petroleum distillates, natural gasor artiii-cial fuel gas, or powdered coa-l, without materially altering the mode of operation as already absorption may beV carried lout according to known methods employing water or aqueous hydrochloric acid solutions as the absorbing medium, and in anysuitabletype of apparatus. If desired, an alkaline absorbing medium, e. g. magnesium hydrate or milk Vof lime, may also be employed, whereby a solution of the corresponding chloride is produced. Thehot acid gases leaving the reaction must be -cooled,*preferably by conducting them through` flues or channels con- Y' structed of refractory siliceous material, such las fire brick or fusedv silica,-before being brought in contact with metallic, glass or enamel surfaces, in order to avoid chemical attack of'such surfaces, or cracking dueV to diiferencesin expansion. When the regenerative principle ofabsorbing heat is employed, as shown in Fig. 2, such coolingof the gases isl advantageously combined with exchange ofl heat between the. incoming' and outgoing gases, thereby promoting the thermal efliciencyof the process. Y y

. ,In thek following claims; the expression dispersed form as applied'toa carbonaceous fuel is intendedk to comprehend'either a,

stateof molecular dispersion, as in the case vof a gaseous fuel, or a state of minute physical dispersion, as in the case of an atomized liquidffuelorof a powdered solid fuel.

Other modes of applying the principle of our invention may be employed instead ofthe one explained, change beingmade as regards or the equivalent of such stated step by. be employed. f

We therefore particularlyk point out. and distinctly claim asA our invention 1. A process for the manufacture of hydrochloric acid which comprises burning a carbonaceous fuel in dispersed form with at least sufficient air for the complete combustionthereof and simultaneously introducing chlorineand water vapor into the `combustion Y zone. Y f n s l Y Y 2. A process for the manufacture of hydrochloric acid which comprises reacting chlorine and water vapor in a heated zone mainplete combustion thereof.

'3'. A process for the manufacture of hydrochloric acid which comprises introducing air, chlorine and water vapor into aheated reaction Zone maintained at a temperature Y between 900?J and 1500o C. by the combustion therein of a carbonaceous fuel in dispersed form with at least suicient air` for the complete combustionthereof and separating hy-` drochloricacid-from the reacted gaseous mixture; 1 i

4. A process'for themanufacture of hydrochloric acid which comprises introducing' air, chlorine, vwater vapor and a carbonace'ous fuel indispersed forni into a heated reaction Zone maintained at a temperature between 900 and 1500D C., such air being in amount sufcient for completecombustion of such fuel, separating hydrochloric acid from the reacted Vgaseous. mixture and preheating the gases entering the'reaction by passing the same .through a zone previously heated by Contact with the-hot reaction gases.

5. A process for-the manufacture of hydron chloric acid which comprises'burning a hydrocarbon with sufficient air for complete combustion thereof inthe presence of chlorine and added water vapor. v

` 6. A process for the manufacture of hydrochloric acid which-comprises burning a hydrocarbon with suificient air for complete combustion thereof the presence of chlorine with addition of water vapor inl amount suiiicient to provide an,v excess thereof in the reaction Zonev over the Aquantity required to combine withall of the chlorine present..`

7. A process for the manufacture of hydrochloric acid which Vcomprises burning ahy- Y drocarbon with sufficient air for the complete combustion thereof to form ,CO2 and H2OV and simultaneously' introducing chlorine thereto in amount relative to the H2O. present less than theoretically required to combine therewith in accordancewith the equaton angosce-Ancud.

8. A process 4for the manufactureofhydroi chloric acid which comprises burning a hydrocarbon with air in sufficient amount for complete combustion thereof and :simultaneouslyintroducing chlorine andwater vapor thereto. v 9. Aprocess for the manufacture of hydrochloric acid which comprises introducing air,

chlorine, water vapor and a hydrocarbon into a heated reaction zone maintained at a teinperature between 9000 and` 1500O C., such-air being inamount sufficient for complete combustion 0f such hydrocarbon, and separating 1 hydrochloric acid from the reacted gaseous mixture. n f

' 10. A process for the manufacture of hydrochloric acid which comprisesintroducing air, chlorine, water vapor and a hydrocarbon into a heated reaction Zone maintained at aV temperature between 9000 and 15000 C., such air being in amount sufficient for complete Y combustion of such hydrocarbon, separating hydrochloric acid fromthe reacted gaseous mixture and preheating the gases entering the reaction by passing the same through a zone previously heated by contact with the hot reaction gases.

11. A process `for the manufacture of hydrochloric acid which comprises introducing air, chlorine, water vapor and a hydrocarbon into a heated reaction zone maintained at a temperature above about 9000 C., such air being in. amount sufficient for complete combustion of such hydrocarbon, and separating Vhydrochloric Vacid from the reacted gaseous mixture. I

12. `A process for the manufacture of hydrochloric acid which comprises reacting chlorine with water vapor in excess of the amount thereof required accordingto the equation;

while maintaining the temperature within the reaction zone between about 9000and 15000 C. by the simultaneous combustion therein of a carbonaceous fuel in dispersed form with sufhcient air for the complete oxidation thereof, and separating hydrochloric acid from the reaction product.

13. A process for the manufacture of hydrochloric acid which comprises reacting chlorine With water vapor in excessief the amount thereof required according to the equation;

while maintaining the temperature with in the reaction zone between about 9000 and 15000 C.' by the simultaneous combustion therein under oxidizing conditions of a hydrocarbon fuel, and separating hydrochloric acid from the reaction product. i

14. A process for the manufacture of hydrochloric acid which` comprises reacting chlorine with water vapor in excess of the amount thereof required equa-tion;

while maintaining the temperature within the reaction Zone between about-9000 and 15000 C. by the simultaneous combustion therein under oxidizing conditions of a hydrocarbon fuel, preheating the gases and vapors entering the reaction by passing the same through a zone previously heated by contact with the' hot reaction gases and separatinghydrochloric acid from the reaction product,

15. A process for the manufacture-of hydrochloric acid whichcomprises Vburning a combustible gas containing carbon compoundsl and hydrogen with sufficient air for the complete combustion thereof, simultaneously introducing chlorine and water vapor into the combustion zone and separating hydrochloric acid from the gaseous reaction product.

16. A process for the manufacture of hydrochloric acid which comprises burning a hydrocarbon oil with suiicient air for the introducing-chlorine and water vapor into the combustion Zone and separating hydro` the gaseous reaction prodaccording to the i complete combustion thereof, simultaneously 

